Compost pile in wire cage and compost bin
Compost is the decomposed remains of organic materials-including leaves, kitchen scraps, and plant remains. Compost contains essentially all the major and minor nutrients plants need to thrive and improves soil structure—the home where plants live.
You cannot add too much compost to your vegetable garden—all of the compost you add will improve crop yield. If possible, spread an inch of compost across planting beds in early spring and again after harvest. If you can spread two inches of compost across the planting area, even better! As well, throw a handful of compost into planting holes at transplant time and later add compost around crops during the growing season as a side-dressing for an extra dose of nutrients.
The best compost is aged compost; it will be blackish brown in color, moist, crumbly, and uniform in texture; the vegetable matter in aged compost will not be recognizable. The nutrients in aged compost—often called humus—will be the most accessible to plant roots. (Leaf transpiration draws the nutrients in humus that has been dissolved in soil moisture into plant roots and up into plant cells to fuel plant growth.) Partially decomposed compost benefits the soil as well; it feed earthworms and soil bacteria that exude plant nutrients as well.
Where to get compost
You can make your own compost or you can buy it bagged at your local garden center.
How to make compost
There are two ways to make compost: aerobic composting allows air to accelerate decomposition; anaerobic composting all but excludes air.
Anaerobic composting can be done simply by piling up garden and kitchen waste as it accumulates into one big pile or building a compost pile one layer at a time—alternating brown and green waste. Layering is the most effective way of anaerobic composting. Layers should alternate between woody, carbon-rich material (browns), and lush, leafy nitrogen-rich material (greens). An optimal layer would be about 6 inches deep; the optimal compost pile would be 3 to 4 feet high and wide. Organic material can simply be piled up or held in a box or cage, lightly sprinkled with water, then covered with a tarp or heavy-duty plastic sheet and left to rot. Complete decomposition will occur in 9 months to a year depending upon the weather. (Solar heat will accelerate decomposition.)
Aerobic composting is accomplished via rapid decomposition. Follow the same layer and compost pile formula used in anaerobic composting, but rather than walking away and allowing time to take its course, aerobic composting calls for turning the compost. Turning introduces fresh oxygen into the pile which re-activates the composting process by giving bacteria renewed energy to decompose organic materials. Aerobic composters seek to keep the center of the compost pile at about 140°-158°F, optimal for decomposition. When the temperature falls below optimal (as measured by a compost thermometer), the pile is turned—as often as once a week. You can turn a compost pile by forking materials on the outside of the pile to the center or by breaking down the pile and rebuilding it layer by layer.
What to compost
Compost is best made from garden cuttings and kitchen peelings and scraps, including fruit scraps, vegetable scraps, coffee grounds, stale bread and eggshells. Do not use meat, bones, or fat, including dairy products in compost piles—these materials will not decompose quickly and will attract insects and vermin.
Keep the compost pile just moist; do not allow it to dry out. Aim for about 50 percent greens (grass cuttings and fruit and vegetable scraps) and about 50 percent browns (dry leaves and twigs, egg boxes and cardboard). If the compost turns wet and sludgy, add more browns, if it is too dry, add more greens.
How to Compost Faster
- Using Compost In the Vegetable Garden
A complete guide to choosing the right compost
- The Dirt On Soil Versus Compost
- Compost, Mulches & Soil Conditioners: What are you really getting?
- Making your own Soil and Potting Mix
- Related Questions
- Tips on Growing Grass Seed With Compost
- Use a Generous Amount of Compost
- Planting the Grass Seed
- Seed Bed Preparation
- Rocky soil? Grow grass using compost
- How to Seed a Lawn
Using Compost In the Vegetable Garden
You’ve probably heard or read that compost is really useful in the vegetable garden, not to say essential. But if you’re not sure when you should use it, and when you should use something else, then read this quick guide, and you’ll be much more confident.
Compost is an ideal way to add organic matter to soil – It doesn’t matter whether it’s home-made or whether you buy it from compost suppliers, as the organic content will be broadly similar. The only question is whether you can make enough for everything you need.
Why should you add organic matter? there are two main reasons:
- The first is that compost improves soil structure. It doesn’t matter whether your soil is sandy or heavy clay, adding organic matter makes it closer to the ideal loam. It adds smaller particles to sand, improving the water retaining properties, and it breaks up a clay soil.
- The second reason is that it adds nutrients. With the best will in the world, and even with a really good crop rotation system, vegetable growing is hungry on the soil. Unless you want to use vast quantities of fertiliser, and most of us don’t, then you’ll need to find a way to put some of the nutrients back again. Compost or manure is the ideal way to do this.
Mushroom compost and mushroom and manure compost are really good sources of organic matter for vegetable gardening, find out more about mushroom composts. But if you do buy compost, make sure that these are from a reputable supplier, and that they treat their compost to remove any spores, unless you really want to start a mushroom farm.
So when you should add compost or manure? Ideally, twice a year, in autumn and spring:
- In autumn, wait until you’ve removed most of the summer crops, leaving only brassicas and any overwintering root vegetables. Spread your compost over the whole area, including around any plants that are left. You don’t even have to dig it in if you don’t want to, as it will gently rot in over winter.
- In spring, again spread it over the whole area. If you’re using manure, particularly if you’re not sure how well-rotted it is, don’t add it to any beds where you’re going to grow root vegetables. Carrots and parsnips won’t grow directly towards manure, so they twist and turn if they meet a bit in the soil. Bizarre, but true.
It’s also really good to add compost when you’re planning to grow particularly hungry vegetables, or ones that need a lot of moisture, such as cauliflowers or celeriac. For these plants, dig a trench about a spade or two’s depth, and fill it with compost or manure before planting.
A complete guide to choosing the right compost
Can I re-use my patio pots year after year?
You can certainly re-use them, but it’s best to tip out all of the old compost and then wash the containers thoroughly with warm soapy water, followed by a good rinse with a solution of cold water and a garden detergent. It’s important to do this because your existing compost may be harboring vine weevil larvae and other garden nasties. It’s far better therefore to have a spring clean and thus minimise the risk of pests and diseases infesting or infecting your new displays.
Why can’t I use my own garden soil to pot up plants?
garden soil doesn’t hold as much water as a good potting compost and so you will have to water more often or your plants will suffer. Soil also lacks essential nutrients and so plant growth will be slower. Garden soil may also harbour pests and diseases.
I’ve opened up my compost and it looks like an insect has laid eggs in it
This is most likely to be the small round coloured granules, which are the controlled release fertiliser, that when squeezed will pop open releasing a liquid which is the fertiliser concentrate. The fertiliser cases have a semi permeable membrane, which allows water inside to dissolve the nutrients within them. The nutrients are then released back into the compost in a soluble form for the plants to absorb. The cases will naturally breakdown in the compost over time.
How can I find out whether my soil is suitable for rhododendrons?
The best way is to use a pH soil testing kit. If the results show your soil is naturally acidic then rhododendrons, azaleas, camellia and the like will thrive. If it’s neutral then you can still plant away, but feed with a special plant food that’s been formulated for acid-loving plants such as Miracle-Gro Water Soluble Ericaceous Plant Food. If you’ve got alkaline soil then your best bet is to plant the rhododendrons in a container filled with a suitable ericaceous compost – try Miracle-Gro Azalea, Camellia & Rhododendron Enriched Compost – and then feed with an ericaceous plant food throughout the Summer.
Can you explain the differences between the John Innes composts?
John Innes Composts are soil-based growing media made from a mixture of loam, sand or grit and peat with increasing amounts of plant foods added. Levington John Innes Seed Compost contains the smallest amount of nutrients as this encourages the best germination and growth of tiny roots and shoots. Levington John Innes No.1 Compost has slightly more nutrients and is for transplanting seedlings. Levington John Innes No.2 Compost for when you are potting up small plants and Levington John Innes No.3 Compost has the most nutrients, as this is designed for final planting up of plants ready for display or cropping.
The Dirt On Soil Versus Compost
Soil is basically the top layer of the earth. Soils are made up of various proportions of sand, silt, clay and small amounts of organic matter (decaying insects, plants, creatures, fungi), as well as minerals and nutrients. These different-sized particles give soil its texture. It is the natural medium in which to grow plants. A publication from the Environmental Protection Agency says there are more than 70,000 types of soil in just the United States. Just don’t call it dirt. Dirt is is mainly ground rock and pebbles; a filler with mainly mineral content but no real nutrients. Dirt smells and looks like dust. Soil is dark and smells earthy.
Soil formation happens when many things interact: air, water, decaying plant life, rock, animal life and chemicals. It forms over a period of up to 1,000 years. Plant roots and lichens break up rocks, which become part of new soil and roots loosen the soil and allow oxygen to penetrate it. Also, earthworms and other organisms live in soil and help loosen or aerate it. If you’re creating new in-ground garden beds or building a raised-bed garden, you’ll need to amend the native soil and in some cases add soil. That’s where compost becomes important.
Compost is the recycling of plant and kitchen waste as a fertilizer and soil amendment. It is dark and crumbly and, when done correctly, smells like good soil. Compost improves soil and plants by returning organic matter to the soil in a usable form. Compost helps break up heavy clay soils, improving its drainage. It makes sandy soil better able to retain water and essential nutrients. Adding organic matter (compost) to soil improves plant growth and is essential for gardens in the Sonoran desert. Improving your soil is the first step toward improving the health of your plants, but compost is not a planting medium; it is a terrific soil amendment.
You can make compost at home, easily. Or you can purchase organic compost at Southwest Gardener or reputable nurseries. If you’d like to start a home compost pile, chapter 6 of “Desert Gardening for Beginners” tells you all you need to know to be successful.
I was watching a discussion on a popular garden forum between two well known seasoned gardeners. They were discussing the difference between “soil” and “compost”. One gentleman said that “soil” was anything consisting of decomposed matter. The other gentleman argued that “soil” was rocks and minerals.
Well, for arguments sake, I’ll have to disagree with both of them.
The second gentleman was only partially right.
What is the difference?
Soil is basically the top 6 inch or so layer of the earth. It’s made up of sand, silt, rock, minerals, gases and even decomposed matter like plant material and dead carcasses from animals and insects (compost). It also includes microbes and fungi know as the food web. All of this matter is considered “topsoil” and sits on the TOP of the earth (hence the name)
Unfortunately, the earth is being rapidly depleted of this resource as commercial farmers scrape the top layer off to remove weeds and level the land. This results in a dead, dry and parched earth. This is where farmers like to plant. But the sad reality is, they are depriving themselves of the best growing medium on the planet. They are then forced to till in fertilizers to replenish what was lost. And then this vicious cycle starts over again year after year.
Compost is basically decomposed plant matter like kitchen waste and rotting plants. It also includes dead shrubs, tree branches, and basically anything living thing that falls to the earth and dies. It is broken down slowly over time and turned back into what many would call dirt. It turns into one of the richest organic fertilizers that money can buy.
So when you hear someone say “I added soil from my compost pile to my raised beds”, what they are really saying is, I added compost to my raised bed from my compost pile 🙂
So to simplify things, You can amend your topsoil with compost to increase its mineral content or to make the soil more loamy for planting, but you never amend your compost with soil. Topsoil will contain compost, but compost does not contain topsoil.
Compost, Mulches & Soil Conditioners: What are you really getting?
How many times have you gone to the nursery wanting to buy something to improve your soil (because that’s what they tell you to do before planting anything) and only come away more confused than before you went in?
There seems to be dozens of bags to choose from: potting mixes, composts, soil conditioners, mulches, manures and that’s just the broad categories! Mixes and blends are then labelled standard, premium, organic, natural, regular, certified, standardized ….. the list goes on. How do you know what’s what?
Well, I recently went along to the briefing seminar for the release of the new Australian Standards on Compost AS4454 (2012) to find out the answer. (I know … I hear you … I really should get a life!) I arrived late thanks to Sydney traffic, and to my surprize, walked into a room packed with men wearing collars and ties …. hardly a woman in sight and my Veggie Lady polo shirt did seem a little out of place. Who’d have thought that composters would dress so formally! I later found out that they were mostly management or laboratory testers. But nevertheless, my curiosity as a backyard gardener and composter was not disappointed.
Compost vs Potting Mix
An important distinction was made early between what is a compost and what is a growing medium. Potting mix is designed for growing plants. A compost is not to be used on its own as a growing medium but is meant to be mixed into the soil instead. As such, a compost will have different levels of mineral balance and moisture holding capacity than a plant growing mix. So, as a home gardener, make sure you always mix bagged compost in with other soil in the garden or with other potting mixes and materials when using it in container gardens, because it could be too strong for your plants and actually do harm to their growth.
The new regulations actually lifted the exacting standard required previously for copper and zinc levels because compost is designed to be incorporated into background soil and not used exclusively as a growing mix. As long as we still have copper water pipes we will continue to have high levels of copper residues unfortunately. Higher levels of zinc and copper were deemed satisfactory when balanced out with other materials or soil under the new standard.
The classification of mulches, composts and soil conditioners is simply defined by the particle size. The definition in decreasing order of size is coarse, fine or soil conditioner.
Mulches are therefore, broadly defined as coarse materials that allow irrigation and rain water to filter through easily. They are mainly woody and will have a higher carbon:nitrogen ratio (you may now find that the C:N ratio figure is listed on the label of the bag). Mulches are meant to sit on top of the soil and not mixed in and will take longer to break down.
Composts contain fine materials and are meant to be dug into the soil. The carbon:nitrogen ratio will be lower indicating that it will have more available nitrogen to feed your plants.
A soil conditioner has even smaller particles and may have higher nutritional value for your plants. It is to be dug into the soil and will break down the quickest. It will also help retain more moisture in the soil.
Classification of composts is further defined by the maturity level. This tells you how much decomposition has taken place and whether or not the compost is still “hot” or fully rotted and ready to use in any situation. It determines the amount of biological activity in the mix as measured by the heat of the mix. The categories are raw, pasteurised, composted or mature.
Raw mulch – indicates that it is a single source of plant material (i.e. it’s only one type of tree that has been shredded into large particles suitable for using as a mulch) and contains no known source of pathogen. No composting has taken place.
Composted materials can still be biologically active and further decomposing can take place when used. It is defined as ready for some commercial landscaping uses where mature plants can withstand further breakdown of materials. For some sensitive or younger plants, a mature mix is necessary.
It’s important to understand the need for pasteurisation in commercial production of compost. Unlike the home compost where fresh kitchen scraps and possible free range home poultry manure can be used, commercial operations depend on the collection of “resource” from waste disposal systems. Food scraps can be left to putrefy for days before collection and animal waste can contain some pathogens that are harmful to humans. Collection is often made from very unsanitary conditions. Plant material collected from kerbside green waste may also contain some diseases that are disastrous for plant survival, e.g. phytophthora or myrtle rust can potentially wipe out whole stands of native flora.
Pasteurisation is a process of heating the materials in order to kill off any of the pathogens that are potential harmful to human health. The unfortunate thing is that it is indiscriminate and will kill off good bacteria as well as bad. In the home garden, compost generally won’t reach the 55oC required for pasteursing and will leave the beneficial micro-organisms in tact. The downside is that home composting won’t kill all harmful pathogens, weed seeds or plant propagules.
To reach effective pasteurisation, a compost heap has to reach a minimum of 55oC lasting for 3 days. This temperature is hot enough to pull your hand away because of the heat given off and is usually only achieved with long windrows that are about 4.5 metres wide and 2 or 3 metres high. The centre of the pile heats up while the outer 300mm layer encompassing the heap will remain cooler. This is why it’s important to turn the heap. The aim is to turn the outer material into the centre of the heap to ensure that all materials are effectively pasteurised. Commercial composters are required to turn the heap 5 times, maintaining temperatures over 55oC for at least 15 days in total to ensure pasteurisation of all material. Re-oxygenating the heap by turning it provides fuel for biological activity and this increased activity generates energy in the form of heat as a result. Pasteurisation is important for the health and safety of the end user.
Labeling of chemical contaminants
Under the labeling guidelines more information is divulged to us as consumers, if the producers choose to list the results of the new testing requirements for contaminants. At first you might be horrified to see levels of mercury, cadmium and other heavy metals listed on your bag of compost. Don’t be put off by this, it’s a good thing. Producers of organic composts now have to test for these under the most vigorous standards that labs can perform. Additional costs for these meant that historically, many compost producers would not perform these tests and composts would slip through with heavy metal levels higher than are now required. If test results comply with standards you can be assured that heavy metals are within safe limits.
Other chemical elements in some composts can be at levels that cause phytotoxicity (i.e. dangerous levels of nutrients that can cause plant death but no significant effect to human health). Compliance with the standards ensure against such phytotoxicity.
It’s not only heavy metals that are tested, it’s also pesticide residue. A bag of compost that displays compliance with the Australian Standard AS4454 (2012) is assured of negligible or non-existent residues. Listing of test readings, although initially confronting for the consumer, actually provide assurance of transparency by the producer. Rather this than the bag of compost that hides the results of these new tests because of failure to meet the standard that ensures your health and safety.
Other listings on the label
Under the new standards you could expect to see the pH level listed on the label. This tells you the acidity or alkalinity of your compost and is good for determining if you want to use the compost on acid loving plants like azaleas and camellias (who need a pH around 4).
Organic carbon levels may also be listed giving you a clear conscience knowing that your choice is helping the environment through increased carbon sequestration.
Take home messages:
Always mix your compost and soil conditioners with soil and don’t use them as a potting mix.
Look for the Australian Standard on the bag for assurance of quality.
AS 4454 gives assurance of no weed seeds or plant progagules.
AS 4454 gives assurance of no pathogens present and is disease free.
Better to have chemical residues and heavy metal levels listed on the label than hidden from the consumer to show safety compliance.
When composting at home, turn your mix to rotate the materials from the outside to the inside.
If your home compost is allowed to dry out before completing the decomposition process, there is a chance of reinfestation of pathogens.
Don’t put diseased plant material into your compost.
Always compost wearing a collar and tie – apparently!
Making your own Soil and Potting Mix
The first thing to note is that most commercial potting mixes are actually growing media that don’t contain soil. Soil varies greatly in composition and texture, whereas potting mix is designed for use in containers and is a mixture of light weight organic and inorganic (mineral) materials that drains freely. In this article, we’ll look at how to make different potting mixes for container gardening and also look at a few ingredients for improving garden soil or for making a mix that can stand alone in a raised garden bed. You can make potting mixes to suit a variety of purposes, such as raising seedlings, rooting cuttings, potting up indoor plants, and for any container gardening outdoors.
One of the best things about making your own mixes is being able to create the perfect growing conditions for your plants. For raising seedlings and rooting cuttings, a light weight and fine textured mixture with mineral components such as perlite that drains freely will work really well, but for growing vegetables you would make a mixture with more organic matter and compost that will hold extra water and nutrients. The basic materials for making your own potting mix or improving your soil are just a few different organic and inorganic (mineral) products.
Well-aged compost or well-rotted animal manure
If you have a compost heap with some mature compost (i.e. compost that is fully decomposed), that makes an excellent ingredient in potting mixes and is also a great addition to improve any type of garden soil, otherwise you can buy (or collect from places like horse stables) some well-rooted manure or mushroom compost. You can test these raw materials for maturity and suitability by sowing some fast germinating seed such as radish. If it grows normally then the material is good to use. In fact this is a quick and simple way to test the final growing mix you come up with.
Again, if you have a worm farm, worm castings make a fantastic addition to potting mixes or to improve garden soil, as they help to create a great soil structure and improve nutrient-holding capacity. The best way to use them is to dry them out first so that they can be more easily mixed with the other ingredients in your home made ‘brew’.
Composted Pine Bark
Composted pine bark helps to aerate the soil and improve water circulation. Its an important part of most commercial potting mixes these days and makes a good addition to mixes for potted trees and shrubs as it does not break down as readily as other ingredients such as compost.
Coir (coconut fibre) sometimes sold as Cocopeat
Coir is a compacted coconut fibre which can be bought in small bricks and then expanded in water to add to potting mixes. It is very light in texture, similar to peat moss, and has a pH close to neutral. 100% coir is perfect for raising seedlings.
Perlite is a volcanic mineral that looks like small styrofoam balls butm is in fact a natural inorganic mineral. It is a basic component in many potting mixes. The puffy little balls allow for a high level of air and water permeability, and perlite is a common ingredient in standard potting mixes and plant propagation mixes.
Sand can be added to potting mixes to improve drainage. Coarse is mainly used for cacti and succulent mixes and can also be used in potting mixes for native plants. Fine sand is better for seed raising mixes as it helps the mix hold a bit of extra moisture. Those are the basic materials you’ll need to make a few simple potting mix recipes. There are many more ingredients you can use when making your own soil or potting mix – it’s a fascinating topic to explore!
Here are a few basic recipes for potting mixes to suit different plants.
Regular Potting Mix
This regular potting mix recipe has a balanced combination of ingredients to retain some water while also providing good drainage. Add some slow-release fertiliser when planting.
- One part composted pine bark
- One part mature compost, worm castings or mushroom compost
- One part perlite
- Add a handful of garden lime or dolomite per ten litre bucket of mix.
Australian Native Potting Mix
Natives will need better drainage than just the regular potting mix, but you can use that as the base and then add sand to improve the drainage, as well as some slow-release fertiliser specifically formulated for natives.
- Two parts coarse sand
- Three parts regular general purpose potting mix.
Seedling Potting Mix
Seedlings need a very light mixture, and this combination has been used successfully by many gardeners to raise seedlings.
- One part coir (coconut fibre)
- One part perlite or fine sand
for Organic Gardens
1. “Compost is a fertilizer.”
This one dies hard, and its persistence points to our cultural ignorance about plants and what sustains them. It persists because there is some truth in it as reluctantly acknowledged in the section revealingly entitled “Adds (a few) Nutrients.”
As admitted in that section, albeit through gritted teeth, compost does contain low levels of primary and secondary nutrients and important quantities of micro-nutrients. However, composts do not usually contain enough of the primary nutrients to qualify as a fertilizer or to satisfy the needs of most plants.
But compost does contribute to plant nutrition, not primarily through the nutrients it contains but through those it makes available to plants.
Just about every gardener knows about the three main fertilizers, the primary nutrients, required by plants: nitrogen (N), phosphorus (P) and potassium (K). These three nutrients so dominate many gardeners’ horizons that nothing can be seen beyond them. Indeed, the misperception has grown up that if something is good for plants it’s because it provides these nutrients. Since compost is good for plants, it must, therefore, be a fertilizer. If it isn’t a fertilizer, how can it be good for plants?
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The development of synthetic fertilizers has encouraged a simplistic approach to agriculture and to gardening: providing the right chemicals solves all our problems. But nutrients alone cannot keep plants healthy if they’re in poor soil. There are several types of poor soils: heavy, clayey soil that doesn’t drain well, sandy earth that won’t hold water, earth that is either very acidic or highly alkaline, earth so compacted that roots can’t move through it easily, or earth low in the bacteria that actually produce nutrients from mineral particles or in the fungi that extend root zones, or earth that can’t hang onto the nutrients that are present or those that are added.
As indicated in the previous section, compost can aid plants in many ways quite independent of its nutrient content. Because it improves soil structure, adds beneficial microbes, and boosts cation exchange capacity (CEC), compost improves the mobility of air, water and nutrients in the soil, all of which make nutrients more readily available to plants.
2. “Compost = Humus”
It’s amazing how many sources still define compost as humus. It’s not. Compost contains humus, which is one reason for its remarkable traits. But if it were entirely humus, our gardening lives would be much easier because we would only need to add it every hundred years or so, instead of once or twice a season.
Think of this as ancient, dinosaur-age compost. Down to Earth® Granular Humic Acid Fertilizer is harvested from a huge deposit of compressed and decomposed plant life from millions of years ago. Encourages microbial life and nutrient uptake. OMRI Listed for use in organic production.
Compost, as noted above, and as every gardener knows to her sorrow, needs to be renewed. It consists of a remarkably complex mix of compounds, elements and living micro-organisms, many of which get used by plants once they are in soil.
Humus, in contrast, can remain unchanged in soil for thousands of years. Humus is the organic material most resistant to decay, ligneous material derived from tough, fibrous and waxy sources. It consists of long, complex molecules that are eaten and excreted by various soil inhabitants over and over again without undergoing any chemical or biological change.
These molecules play important roles in building soil structure. Because they are so long and complicated, they tend to provide plenty of places where other molecules can latch on. They promote soil aggregation, the gathering of soil molecules into small clumps or aggregates. And aggregation is key to maintaining good soil structure.
3. “There’s no such thing as too much compost.”
Some quite reputable people will say this, word for word. The reason, of course, is that most farmers and gardeners are constantly struggling to produce enough compost for their fields and gardens. It’s hard to imagine having too much.
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It’s fairly obvious that smothering a lawn in compost is not a good idea, even if you smother it with organic compost. (Perhaps this is the horticultural equivalent of smothering someone with love?) The recommended application rate for lawns is in fact only 1 cubic yard of compost for every 1,000 square feet, which works out to 1/4th to 1/3rd of an inch in depth. The suggested rate of 1/4″ in depth simply seems too thin. But more actually can smother grass, or at least the part of it closest to the ground. And if you damage that part, chances are you’ll lose the whole plant.
Linda Chalker-Scott, a horticulturist at both Washington University and Washington State University, with experience in forests, landscaping, and gardens, devotes several entries in her “Horticultural Myths” column to proving that one can indeed use too much compost, especially if one uses it where no organic material should be used at all. All of these columns, which originally appeared in Master Gardener Magazine can be downloaded from her website.
Landscapers and gardeners frequently hear that transplanted trees and shrubs should be backfilled with soil that’s been amended (mixed) with organic matter (OM). But Chalker-Scott disputes this in a column from August, 2000. If the hole is dug deeper than the mature tree’s roots will reach, then the OM is simply wasted. Furthermore, if enough (or rather, too much) OM is used, the soil will actually subside as it decays. Finally, the amendment creates a sharp delineation between amended and unamended soil which in turn leads to water problems. (She explains these in detail.)
This logic, according to Chalker-Scott, applies to many landscaping uses of organic matter including compost. She stresses that agricultural fields, which undergo intensive cultivation, need intensive replenishment. Permanent landscaping features do not. Her column from December of 2004 (Amending Your Soil with Organic Matter Will Improve Water Quality in Streams – PDF) outlines the many problems that can result, including water pollution. Too much fertilizer causes nutrient overloading whether the fertilizer comes from synthetics or from compost.
The nutrient content of compost and other organic amendments is much lower than that of most fertilizers. When it is mixed with soil at a ratio of 1:4 or even higher, there’s a huge, but slowly- released nutrient load. Compost increases the nutrients in soil not only by adding those it contains, but also by boosting the activity of microbes that release nutrients already in the soil. The nutrients contributed by compost, therefore, far exceed those actually in it.
Even experienced gardeners often don’t know that good soil contains only about 5% organic matter by weight, which is equivalent to about 10% by volume. (See Chalker-Scott’s myth for March, 2003, Healthy Soil Has High Organic Content – PDF) People overestimate the optimal amount as routinely as they overestimate the amount of fat in milk. Here, as anywhere, it is possible to overdo a good thing.
What products to compost
You will be able to source all of the essential elements in order to build a great compost pile without having to look too far! As long as your carbon to nitrogen ratio is optimal (25-30:1) your compost pile will be breaking down properly. Here are some lists of acceptable additions:
Carbon Rich Material “Browns”
Cardboard (free of dyes)
Stems & twigs
Nitrogen Rich Material “Greens”
Kitchen food waste
Weeds (that have NOT gone to seed)
Things to Avoid
Diseased plant material
Manures from carnivorous animals
As for the rhododendron and holly leaves, you can definitely put them in your compost pile. However, it is a good idea to really chop or shred them up, as they take much longer to break down due to their fibrous and waxy make up. It really depends on how quickly you are trying to create usable compost. It might be a good idea to have a separate pile going that you incorporate those leaves into and another pile that you do not. That way you can have a pile you know will rapidly break down into garden goodness and have yet another ready to use later on. Good luck!
Five great ways to use compost
You can make your own compost, buy it in bags or have it trucked in by the tonne, but some gardeners just aren’t sure how to actually use compost in the garden. Our Garden Basics guide shows that it’s really very versatile stuff.
Composting is a great way to recycle vegie scraps, fallen leaves, lawn clippings and other green garden waste back into your garden. Homemade compost is a beaut money-saver of course, and top quality compost from any source should be dark coloured, smell sweet and have a crumbly texture. It looks a lot like really good, rich soil. It has several really handy uses in the garden, so if you aren’t sure what to do with your compost, try these five options for starters.
1. Use it as mulch
Just spread your compost around garden plants as a mulch, applying it up to 40mm deep, if you like. However, you’ll need a lot of compost to cover your garden beds to that depth with compost, and you’ll probably run out very soon if you don’t have it delivered in bulk.
2. Prepare a garden bed
Dig in plenty of compost and well-rotted manure a couple of weeks before planting out vegie patches or garden beds. Let it all break down for a fortnight or so, then start planting. How much compost do you use per plant? It’s hard to overdose on added compost, so be generous with it. As for the manure, use well-rotted manure that also has been composted (ie, aged) beforehand. Never add fresh manure to garden beds. Good examples of well-rotted manures include ‘milled cow manure’ sold in bags, and Dynamic Lifter, which is pelletised chicken poo. See the bags for the recommended application rates for these manures.
3. Make liquid fertiliser
You can turn compost into liquid fertiliser using a bucket or tub. Just add one part compost to three parts water, give it a good stir, then leave it for three days, stirring a couple of times over this period. Apply the liquid to plants as a gentle plant food. You can use the same batch of compost to make liquid food a couple of times, and at the end of it all just return the old compost to the compost bin, or spread it on the garden somewhere.
4. Turn it into potting mix
Compost can also be combined with other ingredients to make a good homemade potting mix. Mix together 4 parts compost with 1 part shredded sphagnum moss and 2 parts coarse river sand. It’s easiest to mix up a decent batch thoroughly in a wheelbarrow or large, wide tub. You can, if you like, add some slow-release fertiliser granules to boost the mix, and these are fantastic as fertilisers, but admittedly not strictly organic. The sphagnum moss and coarse river sand are available at garden centres.
5. Re-wet your dry soil
We’re still finding out fabulous new uses for compost. Digging compost into extremely dry soils helps to get the soils soaking up water again. Each grain of extremely dry soil is coated with a waxy substance that forms a ‘water-resistant’ coating on the soil grains. Compost is full of tiny micro-organisms, and when compost is mixed into dry soils, these little guys help to break down that waxy, water-repelling coating. Combined with the application of wetting agents such as SaturAid or Wettasoil, compost can be a superb dry soil reviver. So, dig over your very dry soil well with a mattock, spade or fork, add wheelbarrows-full of compost and dig it in well, making sure the compost is evenly spread through the soil. When that job is done, scatter the surface of the soil with the wetting agent grains (following the packet directions for the correct amounts to apply) then soak the soil thoroughly for at least 20 minutes the first time, and keep the soil well-watered with regular long, deep soakings when water restrictions permit.
Tips on Growing Grass Seed With Compost
Compost is an ideal medium to plant along with grass seed and encourage growth. Use it when planting and growing grass seed as a soil-conditioning agent. It helps protect and insulate the grass seed, paving the way for thicker and healthier grass over your lawn in the long run. You can find compost at any local gardening store, or even create your own in your yard made up of organic materials. Keep some key things in mind when growing grass seed with compost, such as soil preparation, using the right amount of compost and how to properly integrate the grass seed with the compost.
Use a Generous Amount of Compost
Plan ahead so you can make sure you have enough compost for your entire lawn. You need a layer about 1/3- to 1/2-inch thick of compost for the entire lawn. Figure out the amount of compost you will need in cubic feet by multiplying the width and length of the grass or seeded area, then multiply that result by 1/3. Find one that is specific to your grass variety, region and soil. It may be a good idea to test the pH of the soil before choosing a compost, so you can decide if you want one to balance out the pH if necessary.
Planting the Grass Seed
Plant grass seed with compost in spring or fall in order to get to maximum amount of cooler weather and natural rain. Especially for the northern half of the United States, planting grass seed with compost in fall is common because the ground is still warm. Keep in mind that you want to integrate the grass seed with the compost with a light raking.
Seed Bed Preparation
It is important to have a well-tilled lawn in preparation of the grass seed and compost. Use a till to loosen up the top four inches of the soil. Layer the compost directly on top of the tilled soil in an even thick layer. Mix it thoroughly with the rake over the entire space of the lawn. Layer the grass seed on top of the compost layer, starting on one side of the yard and working one way. After completing this layer, start from the other side of the lawn and layer more seed to ensure an even coverage of seed. Lightly water in the seed with a soft rain sprayer so as not to disturb the seed placement.
Rocky soil? Grow grass using compost
Q: Should compost be applied to newly-planted grass seed as a top-dress on tightly-packed or rocky soil?
For a cool season grass like (tall) fescue, use a very light amount of compost (less than a 1/16 inch). Keep it irrigated.
Some composts (like McGill SoilBuilder) are more nutrient-packed than others. Be careful of the amount of nitrogen you are adding to the newly-seeded area. Too heavy a hand during nutrient application could burn or even stunt newly-seeded turf. The same is true for synthetic fertilizers.
For a warm season grass like Bermuda, an application of 1/8 inch to 1/4 inch over the next 30 days works. Remember to keep it irrigated. This will help the seed establish.
Most tightly-packed soil consists of clay, which challenges good porosity. Using a soil amendment like compost replenishes soil organic matter. Compost improves porosity, even in a rocky soil, and allows air and water to move through the soil more freely.
This creates an encouraging environment for turf establishment and survival.
Toss a little clover in with the grass seed to help set nitrogen and encourage bees.
How to Seed a Lawn
If you’ve spent the summer lamenting your tattered yard or wishing that your patch of dirt were a blanket of soft blades, you can stop. It won’t get any better, at least not this year. But next spring could be a whole other story if you seed this fall – the perfect time to start a new lawn. In cold-weather climates, fall’s cooler temperatures prevent the seeds from drying out, but there’s still enough sun and rain to help them germinate before going into hibernation for the winter, without the competition of crabgrass and other weeds that die off this time of year. And the best part is that the whole process is a cinch. “Seeding is the easiest thing for a homeowner to do,” says This Old House landscape contractor Roger Cook. “It just takes a little soil preparation, the right mix of seed, and lots of watering.”
Illustration by Gregory Nemec
As with most landscaping projects, preparation is the most critical part of seeding a lawn. The condition of the soil has to be ideal to coax the tiny grass seeds into germinating. That means using well-turned earth with proper drainage and the right chemistry.
To get these conditions, you first need to remove any vestiges of the old lawn. Renting a sod cutter for about $75 to $100 a day allows you to slice off old grass and weeds at the roots. Then it’s time to turn the soil with a rotary tiller, adding sand and compost in successive layers to achieve an ideal mix.
But even with these additions, no soil is ready for seeds if it doesn’t have the right pH. The pH scale measures acidity and alkalinity, denoted by numbers from 0 to 14, with 7.0 being neutral. Grass grows best in soil that has a pH between 6.0 and 7.5. If your soil is too acidic (below 6.0)—a common problem in cooler wet climates like the Northwest and Northeast—you can add lime to bring it up. If it’s mildly alkaline (7.5 to 8.0), a little peat moss, which is naturally acidic, should correct it. Soil that is very alkaline (more than 8.0), which is more likely to exist in dry, hot climates, needs sulfur.
All soil could use a little fertilizer boost to nourish the seeds. Then once the soil is ready, the actual planting is cake. Just throw out the right amount of seeds, gently rake them into the turned earth, and make sure they get enough water to keep on growing.
Test the Soil pH
Photo by Webb Chappell
Put measured amounts of soil and water into the test kit’s plastic test chamber and shake well. Wait a minute or two for the soil to settle and the color to develop.
Hold up the vial and compare the color of the soil solution to the color-coded chart printed beside the test chamber. It should read between 6.0 and 7.5.
If the reading shows a pH lower than 6.0, your soil is too acidic and you’ll need to add lime in Step 5. If it’s above 7.5, the soil is too alkaline. For moderately alkaline soil add peat moss in Step 5; for very alkaline soil, use sulfur.
Remove Rocks and Roots
Photo by Webb Chappell
Using a pointed shovel, dig up all rocks and roots that are visible (shown here) including any stones that won’t fit through the tines of a garden rake. Fill holes and depressions with topsoil dug up from a high spot.
Use a rotary tiller to turn the soil until there are no big clumps or patches of packed earth. Use a fiberglass-handled shovel, which is less likely than wood to split or snap, to dig out rocks.
Add Sand and Compost
Photo by Webb Chappell
Cover the planting area with 1 inch of sand. Use a wheelbarrow to transport it to the site. Distribute it as evenly as possible with a shovel. Use a rotary tiller to incorporate the sand into the topsoil.
Now cover the area with an inch of compost, distributing it in the same manner as the sand. Again, use a rotary tiller to incorporate the compost into the soil and sand.
Amend the Soil
Photo by Webb Chappell
Adding lime, peat moss, or sulfur balances the soil’s pH level and boosts nutrients.
Distribute peat moss with a shovel from a wheelbarrow. For lime or sulfur, apply it with a walk-behind broadcast spreader, set to the appropriate distribution rate. Coat the entire area, making sure you don’t miss any spots.
Next, use the broadcast spreader to apply starter fertilizer to the entire area. Make sure the spreader is adjusted to distribute at the rate outlined on the fertilizer packaging.
Rake the Soil
Photo by Webb Chappell
Use a metal garden rake to carefully work the lime (or sulfur) and fertilizer into the top inch of soil.
Finish-grade the soil by raking it level.
Tip: Don’t try to spread the fertilizer, lime, or sulfur by hand—or mixed together in the spreader—as they must be applied at different, specific rates.
Spread the Grass Seed
Photo by Webb Chappell
Disperse grass seed evenly over the soil, cranking the handle of a handheld broadcast spreader. For larger lawns, use a walk-behind spreader.
Be sure to apply an even amount of seed to the entire area
Rake in the Grass Seed
Photo by Webb Chappell
Take a plastic leaf rake, turn it upside down, and use the back of the tines to gently work the seeds into the soil.
Make short, light strokes. Avoid long sweeping motions, which can redistribute the seeds and cause the grass to grow in uneven patches.
Tip: Don’t compact the seeds with a weighted roller because it will create depressions that collect water.
Photo by Webb Chappell
Immediately after sowing the seeds, lightly water the area with a fan-or oscillating-type sprinkler. Set up one or more sprinklers, or move the sprinkler to ensure that the entire area gets dampened.
For the first 8 to 10 days, water two or three times daily, but only for 5 to 10 minutes. Avoid overwatering, which may wash away the seeds. Once the grass sprouts, water once a day for 15 to 30 minutes. It’s typically best to water in the morning, when there’s less evaporation. Avoid watering in the evening; it can lead to fungal diseases.
Tip: If you’re having an automatic sprinkler system installed, be sure it’s equipped with a rain sensor that prevents it from operating during rainstorms.